The Effect of Porosity Type on the Mechanical Performance of Porous NiTi Bone Implants

2016 ◽  
Author(s):  
Amirhesam Amerinatanzi ◽  
Narges Shayesteh Moghaddam ◽  
Hamdy Ibrahim ◽  
Mohammad Elahinia
Keyword(s):  
Mechanical Properties ◽  
Finite Element ◽  
Shape Memory ◽  
Modulus Of Elasticity ◽  
Geometrical Structure ◽  
Niti Alloy ◽  
Porous Structures ◽  
Bone Implants ◽  
Equivalent Modulus ◽  
Diamond Type

NiTi has been shown to be of great interest for bone implant applications. Introducing porosity to NiTi bone implants is an effective technique to tune their equivalent modulus of elasticity in order to acquire similar value to that of cortical bone. Moreover, such porous implants allow for better tissue ingrowth due to the interconnecting open pore structure. The effect of porosity percentage on the NiTi equivalent modulus of elasticity is well understood. However, the effect of porosity type on NiTi bone implant’s performance, in terms of the geometrical structure and other mechanical properties, has not yet been investigated. To this end, we simulated three porous structures made of shape memory Ti-rich Ni50.09Ti alloy. The effect of porosity type on the NiTi implant’s geometrical structure and mechanical properties was studied using numerical tests. The purpose is to compare three NiTi implants with different kinds of porosities, at a similar level of porosity (i.e., 69 %). The assigned porosity types in this study are Schwartz-type, Gyroid-type, and Diamond-type. Three triply periodic minimal surface (TPMS) models (9mm×9mm×9mm) with the assigned fixed level of porosity (69 %) were designed as CAD files using Solidworks. Each model was meshed, and the convergence study was conducted. The three models were then imported into a finite element package (ABAQUS). A UMAT code developed by IUT (Isfahan University of Technology) group was used to simulate the mechanical behavior of the shape memory NiTi alloy. All boundary conditions and loading conditions were applied to the models. Compressive mechanical tests were simulated in the finite element, and the resultant equivalent modulus of elasticity, elongations, stress, and strain was estimated. The results show anisotropic behavior within the three different porous structures. With the same level of porosity (i.e., 69 %), equivalent modulus of elasticity was observed to be 48.9, 34.8, and 30.2 GPa for Schwartz-type, Gyroid-type, and Diamond-type, respectively. Moreover, the Schwartz-type scaffold was seen to offer the highest stress at plateau start and the lowest residual strain after unloading, in comparison with the other two types of structure.

Mechanical Properties of Hydroxyapatite Doped with Magnesium, Used in Bone Implants

2013 ◽  
Vol 430 ◽  
pp. 222-229 ◽  
Author(s):  
Oana Suciu ◽  
Teodora Ioanovici ◽  
Liviu Bereteu
Keyword(s):  
Mechanical Properties ◽  
Thermal Stability ◽  
Modulus Of Elasticity ◽  
Mechanical Characteristics ◽  
Precipitation Method ◽  
Bone Implants ◽  
Wet Precipitation ◽  
Longitudinal Modulus

Hydroxyapatite is a biomaterial, more exactly a bioceramic, from a category of materials frequently used in bone implants. In order to improve mechanical properties, hydroxyapatite is doped with different chemical substitutes, among which the most used are: Mg2*, Zn 2*, La3*, Y3*, In3* Bi3* CO32-, Si and Mn. In the paper are presented the modality of obtaining hydroxyapatite doped with magnesium through wet precipitation method and also the determination of its main mechanical characteristics. There is also an analysis on the effects of magnesium on the following mechanical properties: density, hardness, longitudinal modulus of elasticity, conductibility and thermal stability.

Fabrication and Surface Modification of Porous Nano-Structured NiTi Orthopedic Scaffolds for Bone Implants

2009 ◽  
Vol 1181 ◽  
Author(s):  
Shuilin Wu ◽  
Xiangmei Liu ◽  
Paul K Chu ◽  
Tao Hu ◽  
Kelvin Wai Kwok Yeung ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Surface Modification ◽  
Shape Memory ◽  
Porous Ceramics ◽  
Bone Implants ◽  
Nickel Ion ◽  
Niti Alloys ◽  
Porous Niti ◽  
Surface Areas ◽  
Good Shape

AbstractNear-equiatomic porous nickel-titanium shape memory alloys (NiTi SMAs) are becoming one of the most promising biomaterials in bone implants because of their unique advantages over currently used biomaterials. For example, they have good mechanical properties and lower Young�s modulus relative to dense NiTi, Ti, and Ti-based alloys. Porous NiTi SMAs are relatively easy to machine compared to porous ceramics such as hydroxyapatite and calcium phosphate that tend to exhibit brittle failure. The porous structure with interconnecting open pores can also allow tissue in-growth and favors bone osseointegration. In addition, porous NiTi alloys remain exhibiting good shape memory effect (SME) and superelasticity (SE) similar to dense NiTi alloys. To optimize porous NiTi SMAs in bone implant applications, the current research focuses on the fabrication methods and surface modification techniques in order to obtain adjustable bone-like structures with good mechanical properties, excellent superelasticity, as well as bioactive passivation on the entire exposed surface areas to block nickel ion leaching and enhance the surface biological activity. This invited paper describes progress in the fabrication of the porous materials and our recent work on surface nanorization of porous NiTi scaffolds in bone grafts applications.

Mechanical Evaluation of Hydroxyapatite Nanocomposites Using Finite Element Modeling

2013 ◽  
Vol 135 (1) ◽  
Author(s):  
Kristopher Doll ◽  
Ani Ural
Keyword(s):  
Mechanical Properties ◽  
Finite Element ◽  
Elastic Modulus ◽  
Aspect Ratio ◽  
Finite Element Modeling ◽  
Graphene Nanosheets ◽  
Bone Implants ◽  
Graphene Nanosheet ◽  
Computational Framework ◽  
Element Modeling

Hydroxyapatite (HA) has been proposed as a candidate material for bone implants because of its similarity to the inorganic phase in bone. However, due to its lower mechanical properties compared to bone, it has not been used in load bearing bone implants. Inclusion of second phase reinforcements in HA such as carbon nanotubes (CNT) and graphene nanosheets is expected to significantly improve its mechanical properties. In this study, a computational framework that will improve the understanding of the mechanical behavior of graphene nanosheet and CNT-reinforced HA-nanocomposites is proposed. The variation of elastic modulus of HA-nanocomposites is assessed based on the nanofiller type, volume fraction, alignment, area, thickness, and aspect ratio using the finite element modeling. The results of the simulations show that graphene nanosheets are more effective in improving the elastic modulus of nanocomposites than CNTs at similar volume fractions. HA-nanocomposites reinforced by graphene nanosheets exhibit transversely isotropic material properties and provide the highest elastic modulus when aligned along a direction or randomly distributed in a plane, whereas CNTs provide the best reinforcement when aligned along an axis. Variation in graphene nanosheet area, thickness, aspect ratio, and carbon nanotube length have negligible effect on elastic modulus of the HA-nanocomposite. In addition, comparison between the finite element simulations and theoretical calculations show that clustering of nanoinclusions reduces the effectiveness of the reinforcement they provide. The simulation results and the computational framework presented in this study are expected to help in determining the best design and manufacturing parameters that can be adapted for developing HA-nanocomposite bone implant materials.

Dynamic Characterization of Shape Memory Alloys for Integration With Electronic Packaging

2001 ◽  
Author(s):  
Shivananda P. Mizar ◽  
Ryszard J. Pryputniewicz
Keyword(s):  
Shape Memory Alloys ◽  
Shape Memory ◽  
Modulus Of Elasticity ◽  
Electronic Packaging ◽  
Niti Alloy ◽  
Thermomechanical Behavior ◽  
Detailed Knowledge ◽  
New Approach ◽  
Temperature Changes

Abstract Integration of Shape Memory Alloys (SMAs) with electronic packaging depends on detailed knowledge of thermomechanical behavior of SMAs. In this paper, thermomechanical behavior of SMAs is studied using a new approach based on Analytical, Computational, and Experimental Solutions (ACES) methodology. More specifically, variation in modulus of elasticity of equiatomic NiTi alloy is studied, as a function of temperature. The results show that the modulus of elasticity of the NiTi alloy studied herein varies from 38 GPa to 72 GPa as the temperature changes from −15°C to 190°C, corresponding to phase transition from martensite to austenite. Comparison of analytical, computational, and experimental results shows good correlation.

An experimental and numerical investigation on active compliant joint made by shape memory alloy actuator

2019 ◽  
Vol 234 (2) ◽  
pp. 156-164 ◽  
Author(s):  
Babak Katanchi ◽  
Alireza Fathi ◽  
Mostafa Baghani ◽  
Hamed Afrasyab
Keyword(s):  
Finite Element ◽  
Numerical Model ◽  
Shape Memory ◽  
Numerical Models ◽  
Niti Alloy ◽  
Experimental Tests ◽  
Finite Element Program ◽  
Heating Source ◽  
Compliant Joint ◽  
Actuator Performance

In this paper, a novel active compliant joint for robotic and microdisplacement applications is investigated numerically and experimentally. The proposed actuator structure is simple and possesses a higher energy density compared to the available actuators. Experimental tests are performed employing the shape memory behavior of NiTi alloy by the electric current as a heating source. To verify the actuator performance, numerical models are simulated in a nonlinear finite element program through employing a user subroutine according to experimental tests. Finite element implementation of the proposed actuator is performed based on the constitutive equations developed in Boyd–Lagoudas phenomenological model. Comparing the test and numerical results revealed that the numerical model is successful in predicting the actuator response. Finally, based on the verified numerical model, the effects of different parameters, e.g. the compression spring stiffness on the actuator performance are studied, and an optimal design for the actuator structure is proposed.

scholarly journals Mechanical Properties of Small Clear Specimens of Eucalyptus globulus Labill

Materials ◽  
2020 ◽  
Vol 13 (4) ◽  
pp. 906 ◽  
Author(s):  
Jorge Crespo ◽  
Almudena Majano-Majano ◽  
Antonio José Lara-Bocanegra ◽  
Manuel Guaita
Keyword(s):  
Mechanical Properties ◽  
Finite Element ◽  
Modulus Of Elasticity ◽  
Eucalyptus Globulus ◽  
Wood Products ◽  
Added Value ◽  
Hardwood Species ◽  
Structural Applications ◽  
Numerical Finite Element ◽  
Tangential Directions

Eucalyptus globulus Labill stands out as one of the hardwood species produced in Europe with prominent mechanical properties, which is undergoing a growing interest in extending added value. The development of engineered wood products with this species and its application in timber structures involving numerical finite element simulations requires knowledge of the mechanical properties for the different orthotropic material directions. The aim of the present study is to determine the main mechanical properties of E. globulus from small clear specimens, necessary for the development of finite element models. The work provides experimental results on the ultimate capacity and modulus of elasticity considering different stresses: tension parallel and perpendicular to the grain, compression parallel and perpendicular to the grain (in radial and tangential directions), shear and longitudinal static bending. The work is complemented with experimental data on timber-to-timber friction coefficients for 0°, 45°, and 90° orientation angles, which are useful in the modeling of traditional joints. Very high values of ultimate stress and modulus of elasticity for the different mechanical properties were obtained, highlighting the great potential of this species for structural applications.

Target Shape Optimization of Functionally Graded Shape Memory Alloy Compliant Mechanism

2016 ◽  
Author(s):  
Jovana Jovanova ◽  
Mary Frecker ◽  
Reginald F. Hamilton ◽  
Todd A. Palmer
Keyword(s):  
Mechanical Properties ◽  
Shape Memory ◽  
Young’S Modulus ◽  
Modulus Of Elasticity ◽  
Compliant Mechanism ◽  
Young's Modulus ◽  
Functionally Graded ◽  
Nsga Ii ◽  
Target Shape ◽  
Young’S Modulus Of Elasticity

Nickel Titanium (NiTi) shape memory alloys (SMAs) exhibit shape memory and/or superelastic properties, enabling them to demonstrate multifunctionality by engineering microstructural and compositional gradients at selected locations. This paper focuses on the design optimization of NiTi compliant mechanisms resulting in single-piece structures with functionally graded properties, based on user-defined target shape matching approach. The compositionally graded zones within the structures will exhibit an on demand superelastic effect (SE) response, exploiting the tailored mechanical behavior of the structure. The functional grading has been approximated by allowing the geometry and the superelastic properties of each zone to vary. The superelastic phenomenon has been taken into consideration using a standard nonlinear SMA material model, focusing only on 2 regions of interest: the linear region of higher Young’s modulus of elasticity and the superelastic region with significantly lower Young’s modulus of elasticity. Due to an outside load, the graded zones reach the critical stress at different stages based on their composition, position and geometry, allowing the structure morphing. This concept has been used to optimize the structures’ geometry and mechanical properties to match a user-defined target shape structure. A multi-objective evolutionary algorithm (NSGA II - Non-dominated Sorting Genetic Algorithm) for constrained optimization of the structure’s mechanical properties and geometry has been developed and implemented.

scholarly journals Estimation of Young’s Modulus of the Porous Titanium Alloy with the Use of Fem Package

2015 ◽  
Vol 15 (4) ◽  
pp. 29-37 ◽  
Author(s):  
G. Rotta ◽  
T. Seramak ◽  
K. Zasińska
Keyword(s):  
Mechanical Properties ◽  
Finite Element Method ◽  
Finite Element ◽  
Titanium Alloy ◽  
Biomedical Applications ◽  
Total Porosity ◽  
Porous Titanium ◽  
Pore Shape ◽  
Porous Structures ◽  
Laser Melting

Abstract Porous structures made of metal or biopolymers with a structure similar in shape and mechanical properties to human bone can easily be produced by stereolithographic techniques, e.g. selective laser melting (SLM). Numerical methods, like Finite Element Method (FEM) have great potential in testing new scaffold designs, according to their mechanical properties before manufacturing, i.e. strength or stiffness. An example of such designs are scaffolds used in biomedical applications, like in orthopedics’ and mechanical properties of these structures should meet specific requirements. This paper shows how mechanical properties of proposed scaffolds can be estimated with regard to total porosity and pore shape.

scholarly journals Finite element analysis of Ti6Al4V porous structures for low-stiff hip implant application

2021 ◽  
Vol 12 ◽  
pp. 12
Author(s):  
Porika Rakesh ◽  
Bidyut Pal
Keyword(s):  
Mechanical Properties ◽  
Finite Element Analysis ◽  
Finite Element ◽  
Hip Implants ◽  
Porous Structures ◽  
Element Analysis ◽  
Hip Implant ◽  
Femur Bone ◽  
Body Center Cubic ◽  
Effective Mechanical Properties

Solid metallic hip implants have much higher stiffness than the femur bone, causing stress-shielding and subsequent implant loosening. The development of low-stiff implants using metallic porous structures has been reported in the literature. Ti6Al4V alloy is a commonly used biomaterial for hip implants. In this work, Body-Center-Cubic (BCC), Cubic, and Spherical porous structures of four different porosities (82%, 76%, 70%, and 67%) were investigated to establish the range of ideal porosities of Ti6Al4V porous structures that can match the stiffness of the femur bone. The effective mechanical properties have been determined through Finite Element Analysis (FEA) under uniaxial compressive displacement of 0.32 mm. FEA predictions were validated with the analytical calculations obtained using Gibson and Ashby method. The effective mechanical properties of 82%, 76%, 70%, and 67% porous BCC and Cubic structures were found to match the mechanical properties of cortical bone closely. They were also well comparable to the Gibson-Ashby method-based calculations. BCC and Cubic porous structures with 67–82% porosity can mimic the stiffness of the femur bone and are suitable for low-stiff hip implant applications.

Evaluation of mechanical properties of Ti-25Nb BCC porous cell structure and their association with structure porosity: A combined finite element analysis and analytical approach for orthopedic application

2021 ◽  
pp. 095441192110113
Author(s):  
Soham Chowdhury ◽  
Amit Anand ◽  
Adhish Singh ◽  
Bidyut Pal
Keyword(s):  
Mechanical Properties ◽  
Finite Element Analysis ◽  
Finite Element ◽  
Mechanical Performance ◽  
Bone Ingrowth ◽  
Structural Parameters ◽  
Cell Structure ◽  
Porous Structures ◽  
Element Analysis ◽  
Functional Relationships

Ti-based alloys have been commonly employed in manufacturing implants for orthopedic applications. Binary Titanium-Niobium (Ti-25Nb) alloy is a promising material for potential applications in orthopedics because of their lower elastic moduli and superior biocompatibility than the conventional Ti-based alloys. Implants with porous structures encourage bone ingrowth and reduce the effect of stress-shielding further. This study is aimed at establishing the relationship between the mechanical performance and structural parameters of porous body-centered-cubic (BCC) structures made up of Ti-25Nb (25% by wt.). Solid models of BCC porous structures were constructed (unit cell size: 2 mm; overall size: 8 × 8 × 8 mm3). Finite element analysis (FEA) of the BCC structures with porosity ranging from 29% to 79% (seven porosities) was conducted under tension, bending, and torsional loads. The Gibson-Ashby model and Exponential regression model were also employed to determine the stiffness of the above porous structures. The functional relationships between effective Young’s modulus, effective yield strength, and porosity generated from both the models were found to match the FEA results well. Results indicated that porosity in the range of 50%−70% can be used to design graded porous stems to mimic the mechanical properties of cortical bone.

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